This invention relates to an improved process for the recovery of bound mercury from exhausted mercury-containing catalysts.
In German Pat. DAS No. 1,205,705 there is described a process and apparatus for the recovery of metallic and/or bound mercury from inactive, mercury-containing catalysts in which the catalysts are heated to 270.degree.-600.degree. C. while passing therethrough a carrier gas, preferably hydrogen, at the same temperature range, preferably 270.degree.-350.degree. C. The mixture of carrier gas and desorption gas is then withdrawn and cooled. The mercury is recovered in the form of metallic mercury. In contrast thereto, if the thus-recovered mercury is to be produced in the form of mercury(II) chloride, chlorine is introduced into the mixture of the carrier gas and the desorption gas prior to the cooling thereof, and the temperature is preferably maintained at 300.degree.-400.degree. C. during the desorption.
As a result of their particular use, the inactive, mercury-containing catalysts contain as impurities varying amounts of various organic compounds. In the process described by the German patent, these impurities result particularly during the recovery of mercury in the form of mercury(II) chloride and primarily at the outlet of the reactor and in the wet section of the plant, in the deposition of carbon black and solid and oily organic compounds, along with undesired metallic mercury and insoluble mercury(I) chloride.
It is an objective of the present invention to prevent these depositions and thus improve the recovery of mercury(II) chloride. Other objects will be apparent to those skilled in the art to which this invention pertains.